Low power electric motors of this type are usually employed in household appliances, servo controls, etc., thanks to their simple construction, low cost and to the good speed regulation characteristics allowed. More particularly the electric motors of the prior art comprise a rotor suitably supported by bearings and rotating in the field generated by two or more permanent magnets fastened to the stator or armature and producing the so called stator field. The known constructions provide for a stator structure formed by a metal tubular body into which there are glued or otherwise fastened the permanent magnets and into which a rotor, suitably supported with respect to the tubular structure, is mounted. This known and widespread construction has a number of shortcomings, mainly due to the tubular shape of the outer structure. This latter requires difficult machining with a cost not negligible when compared with the final cost of the motor. Moreover, due to the brittleness of the material of the permanent magnets, the electric motors are not easy to be assembled and have inconveniences during their use. First of all glueing the material means an additional step and is not the best way to fasten the tubular structure or frame and the magnets together. On the second hand the dimensional tolerances for the magnets must be rather close in order that the air gap between the magnets and the rotor has the desired dimensions, and this is not easy to obtain because of the nature of the materials (ferrites) from which magnets are normally formed and of the thermal treatment they undergo.
As for the working, should the magnets break or splinter because of an impact, usually the motor is permanently damaged by the splinters falling into the air gap.
A further inconvenience comes from the magnetic continuity (i.e. the closed magnetic path) of the tubular member which favours the demagnetization of the permanent magnets under overload conditions, thereby reducing the motor performance.
The improved electric motor of the invention substantially eliminates the above incoveniences and achieves additional advantages, particularly as pertains to the temperature control.